In the conventional field-effect transistors, there exist the following drawbacks.
1. Particularly, in field-effect transistors in which the effective base width is determined by impurity diffusion length or by the difference between impurity diffusion lengths, it has been very difficult to attain desirable high frequency characteristics due to intrinsic characteristics determined by said effective base width. PA1 2. Parasitic capacitance or feedback capacitance between gate and drain, or parasitic capacitance between drain and base, or between gate or drain and other electrodes cannot be reduced to a negligible extent, wherefore these parameters affect frequency characteristics, stable amplification and the like. PA1 3. Various functions are affected by the accuracy of photoengraving dimensions and photoengraving positioning. PA1 4. Fluctuation of drain or collector resistance is relatively large.